^ You're right that day and night come from a body's rotation. Because the moon is tidal locked to the Earth, its rotation takes the same amount of time as its orbit, about 28 days. So a lunar day is 28 days. Day and night cycles on the moon match the cycles of the moon seen from Earth - when we see the moon waxing and then waning across successive nights, we're seeing the very long progression of a single Lunar day.

It does lead to rather frequent eclipses! We experience between 2 to 5 lunar eclipses a year. For us, we see the moon disappear in a lunar eclipse as the moon moves into the earth's shadow. From the perspective of someone on the moon, they'd see the sun disappear behind the earth. So for every 6 lunar days, the moon is virtually guaranteed at least one eclipse where the sun disappears.

"Just as you touch the energy of every life form you meet, so, too, will will their energy strengthen you. Fail to live up to your potential, and you will never win. " --- The Old Man at the End of Time

Sonic# described this pretty well already. But yes, that's exactly my understanding as well (of note... in high school I was originally planning on going into astronomy until I changed gears towards economics instead... I never stopped enjoying learning about the stars, planets, and moons though -- only down-side is that I don't have strong astrophysics knowledge).

Anyway, I have a theory then on how this works for Lunar / The Blue Star. This is basically going to be an extension of "a goddess did it". See, Lunar's gravity appears Earth-normal (both from the fact that people move around on it like on Earth, and the fact that it can retain an atmosphere). So during the process of making it habitable for humans, Althena increased the mass enough to raise its gravity up to 1g. Because of this, the Blue Star - Lunar system went from a planet-moon system to a binary planet system, where the two bodies are tidally locked to one another and orbit around a common barycenter (this is the same configuration as Pluto and Charon, except for the Blue Star and Lunar the barycenter would be about equidistant between the two instead of closer to the primary).

That would explain (1) why Lunar is habitable, (2) why the Blue Star always shows the same face to Lunar, (3) why the Blue Star is in the same position in the sky from the perspective of Lunar, and (4) why the day/night cycle is not 4 weeks on Lunar. Now, I haven't done the calculations to figure out how fast they need to be orbiting around one another to do this, but I suspect that Althena would've sped that up too so that the two planets don't crash into one another, and I'll bet that speed amounts to one day / one orbit taking close to 24 hours.

...this works out almost too well. That's it. I'm declaring it canon. KF

Incidentally, I recently read a planetologist's definition of a planet as having sufficient gravity to keep its shape, or something like that. (Context was Pluto's planethood or lack thereof, of course.)

Assuming she made the entire moon more dense rather than magically making people heavier, tides would be higher, assuming they were the same distance apart. Certainly coastal biomes would be the most affected, though I can imagine sea life adjusting to the new patterns. Otherwise, I don't know that the effects would be that bad.

If the gravity weren't so high, Kyle's acrobatics would be more amusing. Dramatic leap followed by a slower landing down to creatures that would have time to prepare. He would hold out his hand, and the sword would hit it after a couple more beats.

"Just as you touch the energy of every life form you meet, so, too, will will their energy strengthen you. Fail to live up to your potential, and you will never win. " --- The Old Man at the End of Time

Alunissage wrote:*chuckle* Well done. Incidentally, I recently read a planetologist's definition of a planet as having sufficient gravity to keep its shape, or something like that. (Context was Pluto's planethood or lack thereof, of course.)

Yeah, the new IAU definition (after finally getting rid of Pluto from the list -- I love Pluto but it's no more a planet than Ceres) includes three things: (1) sufficient mass so that its gravity overcomes the composition of its materials [i.e., it's round]; (2) orbits the sun [i.e., no moons, but binary systems like Pluto-Charon aren't excluded per se], and (3) clears its orbit [i.e., not in asteroid or Kuiper belt -- this one is the most controversial]. Our new Blue Star-Lunar system would be a binary system. Assuming its a magical evolution of the Earth-Moon system, both bodies would then qualify as planets.

Oh, also, bodies have to be really small to not meet the "round" definition. Nearly all asteroids are like this -- only 3-4 known ones are round (Ceres, Vesta, Pallas, and maybe Hygiea which is oblong).

Leo wrote:If Althena increased Lunar's mass to raise its gravity up to 1g, how drastic of an impact would it have on the very planet she's trying to revive?

Hm, Sonic# touched on this a bit. Very early in Earth's history, shortly after the moon formed, it was a lot closer to Earth than present day and had a significant effect on not just water levels but also rock formations. So, increased gravity between the two might cause some elevated mountain ranges close to the part of Lunar that's closest-facing to the Blue Star and vice versa (since they're tidally locked, this is the same point on both planets), but not enough to cause, like, rocks or even water falling upward or anything. Tides would also be somewhat affected but, again, since it's the same point on the two planets rather than a rotation about an axis, the effect might be pretty minor and concentrated. Also, rock formations affected by the gravity would likely take millions of years to form; best we can tell, civilization on a habitable Lunar only goes back 10000 years at best. KF

Kizyr wrote:Sonic# described this pretty well already. But yes, that's exactly my understanding as well (of note... in high school I was originally planning on going into astronomy until I changed gears towards economics instead... I never stopped enjoying learning about the stars, planets, and moons though -- only down-side is that I don't have strong astrophysics knowledge).

Anyway, I have a theory then on how this works for Lunar / The Blue Star. This is basically going to be an extension of "a goddess did it". See, Lunar's gravity appears Earth-normal (both from the fact that people move around on it like on Earth, and the fact that it can retain an atmosphere). So during the process of making it habitable for humans, Althena increased the mass enough to raise its gravity up to 1g. Because of this, the Blue Star - Lunar system went from a planet-moon system to a binary planet system, where the two bodies are tidally locked to one another and orbit around a common barycenter (this is the same configuration as Pluto and Charon, except for the Blue Star and Lunar the barycenter would be about equidistant between the two instead of closer to the primary).

That would explain (1) why Lunar is habitable, (2) why the Blue Star always shows the same face to Lunar, (3) why the Blue Star is in the same position in the sky from the perspective of Lunar, and (4) why the day/night cycle is not 4 weeks on Lunar. Now, I haven't done the calculations to figure out how fast they need to be orbiting around one another to do this, but I suspect that Althena would've sped that up too so that the two planets don't crash into one another, and I'll bet that speed amounts to one day / one orbit taking close to 24 hours.

...this works out almost too well. That's it. I'm declaring it canon. KF

The illustration of Pluto and Charon orbiting each other (starts around 3:30 in the video) reminds me quite a bit of the proportions we see in the title screen of EB, which is clearly way off from how the Earth and the Moon actually relate to each other. (See around 2:15 in the video for the Earth and the Moon.)

The illustration of Pluto and Charon orbiting each other (starts around 3:30 in the video) reminds me quite a bit of the proportions we see in the title screen of EB, which is clearly way off from how the Earth and the Moon actually relate to each other. (See around 2:15 in the video for the Earth and the Moon.)

Oh I'm so used to images of the Earth and Moon being stylized (i.e., distances being decreased to make things actually visible) that I didn't even think of the opening title screen being to scale. Nevertheless, I love videos like this -- especially once you start getting into interstellar space. On a similar note, this is also one of my favorite sites on the subject:http://htwins.net/scale2/(there is also a more recent scale of the universe that shows our own galaxy extending out through the local group, local supercluster, and on up to the entire known universe, but I can't find it at the moment...)

Both the Earth-Moon and Pluto-Charon systems are unique in our solar system for having satellites that are so large in proportion to the main body, so the comparison is fitting. But yes, the Pluto-Charon distance is way smaller -- though the images in the YouTube video you linked definitely illustrate what I'm talking about with respect to how our theorized Blue Star - Lunar system being tidally locked to one another explains a lot about what we see in the games. KF